The production of metal coupons and plates is necessary for many industrial applications. One important application is the manufacture of plates of fissile material that are to be subjected to rolling operations in order to create foils for use as nuclear reactor fuel elements. Traditional methods for manufacturing such metal plates include the steps of: casting an ingot, applying a thermal (softening) treatment, rolling the ingot with a break-down mill (to a thickness suitable for feeding a foil mill), annealing the rolled plate, and cutting the plate into coupons that can be used to feed a foil mill. In such processes, it is desirable to begin with very thin castings in order to minimize the amount of rolling operations that must be performed on the castings. For many applications it would be desirable to cast metals as sheets that have a thickness that is less than 0.020 inches. Historically, the casting of such thin metal sheets has been difficult. When traditional casting processes are applied to the casting of thin metal sheets, the resulting sheets often have unacceptable quality defects. For example, the resultant castings often have excessive porosity, and/or have incomplete extension (i.e., the molten metal solidifies before filling the mold cavity), and/or have cold shunts (i.e., areas where two or more portions of the molten metal have flowed together but did not fuse together before solidifying). When thicker castings are used, rolling operations often result in “alligatoring” (sometimes referred to as “fish-mouthing”), which refers to a splitting of an edge of a rolled metal slab in which the plane of the split is parallel to the rolled surface. What is needed therefore are improved methods for casting thin metal plates and sheets that may be more productively used in subsequent rolling operations.